Severe Thunderstorm Watch 621

Issued

Aug 20, 2007, 1:19 PM EDT (17:19 UTC)

Expired

Aug 20, 2007, 8:39 PM EDT

In force

7 hr

Issued by

the Storm Prediction Center

Largest hail expected

2 in

Strongest gust expected

60 kt

The Cincinnati radar (KILN), 119 km from the middle of the area, began a volume at 17:22 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

Two or more tornadoes

10%

One or more EF2 to EF5 tornadoes

5%

Ten or more severe wind reports

50%

One or more gusts of 65 knots or more

10%

Ten or more severe hail reports

30%

One or more hailstones of 2 inches or more

5%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1816Aug 20, 12:18 PM EDT
• Mesoscale Discussion 1819Aug 20, 4:24 PM EDT
• Mesoscale Discussion 1821Aug 20, 7:11 PM EDT

000
WWUS20 KWNS 201721
SEL1  
SPC WW 201721
INZ000-KYZ000-MDZ000-OHZ000-PAZ000-WVZ000-210100-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 621
NWS STORM PREDICTION CENTER NORMAN OK
120 PM EDT MON AUG 20 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 

       SOUTHEAST INDIANA
       NORTH CENTRAL AND NORTHEAST KENTUCKY
       EXTREME WESTERN MARYLAND
       OHIO
       WESTERN PENNSYLVANIA
       NORTHERN  AND CENTRAL WEST VIRGINIA

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 120 PM UNTIL 900
PM EDT.

HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 70
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST
SOUTHWEST OF DAYTON OHIO TO 30 MILES SOUTH SOUTHEAST OF LATROBE
PENNSYLVANIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...THUNDERSTORMS ARE EXPECTED TO CONTINUE DEVELOPING AND
INTENSIFY PRIMARILY ALONG/SOUTH OF EXISTING STORMS FROM NRN INDIANA
EWD ACROSS OH INTO WRN PA AND NRN WV.  THIS REGION IS RAPIDLY
WARMING AND DESTABILIZING AND VISIBLE IMAGERY SHOWS INCREASING
CU/TCU FIELD INDICATING CAP IS LIKELY WEAKENING.  DYNAMIC FORCING
ASSOCIATED WITH VORTICITY MAX MOVING ACROSS IL IS SPREADING
DOWNSTREAM INTO THE OH VALLEY.  30-40 KT LOW/MID LEVEL WINDS
EXHIBITED ON AREA VAD DISPLAYS WILL PROVIDE SUFFICIENT VERTICAL
SHEAR FOR SEVERE STORMS TO DEVELOP.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM
MOTION VECTOR 25030.


...WEISS

Severe Thunderstorm Watches in Ohio, 2007Severe Thunderstorm Watches in West Virginia, 2007Severe Thunderstorm Watches in Kentucky, 2007Every severe thunderstorm watch in 2007

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.